A person who will attempt to make you repeat what you just said to give them a little more time to think of something to smart to say and/or make you look dumb for repeating yourself.
Usually using the guise that they didn't hear or understand you, this is becoming extremely common.
Hard to defend against, but sometimes just waiting a minute or calling their bluff may win the day.
you: "hey dude what happened to that cute girl you were gonna ask out"
you: "i said where's that cute girl that you were.."
staller: "o that GIRL, she died"
you: "fuck off you heard me the first time"
you: "hey would it be okay if I went and finished that job?"
staller: "what did you say?"
you: "you heard me"
staller: "yeah, no that would be a good idea"